Att bygga en stamdatabas för gotländsk tall
Today's Swedish large-scale forestry uses almost exclusively computer-aided bucking. It allows the harvester computer, using an optimisation price list (steering price list), to maximize the value of each tree. The optimisation price list can be adjusted so that the industry gets the raw material it demands from the forest.
There are various simulation programs that can be used when constructing a optimisation price list. The simulation program merchandise a database of stem shapes using a given price list and mimics a harvester's work. To get the demanded raw material for the industry it is important to use a well-adjusted optimisation price list. To be able to construct a good price list it is essential to have a stem shape data base that resembles the forest were the optimisation price list will be used. No such data base was available for the pine forest from the island of Gotland.
Data collected from a harvester was used and manipulated to create the data base. The data base was merchandised using a simulation program. The result after merchandise was compared with the result from actual harvest operations using the same price list. The database was manipulated further until the results were consistent with results from the harvesting on Gotland.
It proved to be difficult to create a data base that resembles the pine forest on Gotland. A large amount of forced bucking (without computer assisted bucking) was found in the material. The result from the harvested timber from Gotland gave no longer a desirable outcome. The large amount of forced bucking is probably due to the very crooked forest that grows on Gotland in combination with the steering price lists used. To avoid reversing the harvester head before each log was bucked, the harvest operators instead chose to buck manually.
Adjusting the steering price list should reduce the amount of forced bucking. A possible way is to create an optimisation price list, which manages two matrixes; one for straight trees of high quality and one for crooked trees of inferior quality. Before bucking a tree, the matrix that best fits the tree is chosen.